The present invention generally relates to a method of processing vegetable protein to enhance the solubility and color characteristics of the vegetable protein while also reducing the antigenicity of the vegetable protein. More particularly, the present invention relates to a method of chemically treating vegetable protein, such as full fat, low fat, or defatted native soy proteins, to enhance the solubility and color characteristics of the vegetable protein while also reducing the antigenicity of the vegetable protein.
Over the years, researchers have learned soybeans may be processed to recover or extract a number of valuable components, such as soy protein and soybean oil, from the soybeans. Also, soybeans may be processed to form soy flours, soy flakes, and soy meal that are high in nutritionally beneficial substances, such as fiber and protein. Consequently, many soy products are commonly used for production of animal feeds and food products for human consumption.
However, soy products that contain soy protein, prior to appropriate processing, generally have off-flavors that are unpalatable to animals and humans alike. Also, soy products that contain soy protein, prior to appropriate processing, generally contain antigenic substances. Destruction of antigenic substances naturally present in soy products beneficially enhances the digestibility and nutritional benefits of soybean products.
Minimizing both off-flavors and antigenic substances is desirable to increase the value of soy products that contain soy protein. Processing techniques that employ organic solvents are available that beneficially reduce off-flavors present in soy products that contain soy protein. Likewise, processing techniques that employ heat treatment are available that beneficially reduce off-flavors present in soy products that contain soy protein. However, such heat treatment processes do little, if anything, to reduce the antigenicity of the heat-processed soybean products.
Furthermore, such organic solvent-based processing techniques and heat treatment processes typically denature a substantial amount of the soy protein and undesirably yield soybean products with low solubility in water, such as a Protein Dispersability Index on the order of about 7, or even less. The Protein Dispersability Index (subsequently referred to as “PDI”) is a measure of protein solubility (and consequently a measure of protein dispersability) in water. PDI decreases as the degree of protein denaturation increases, absent other processing to enhance the solubility of the denatured protein. Enhanced solubility and dispersability of denatured proteins is important to support production of animal feeds, food products, and beverages that contain proteins derived from vegetable sources, such as soybeans. Another concern is that some existing organic solvent-based processing techniques have a discoloration effect that yields soybean products with off-colors. Off-colors in soybean products, as compared to lighter and whiter colored soybean products, tend to reduce the visual appeal of the soybean products.
The food and animal feed manufacturing industries are in need of a new soybean processing technique that, compared to existing techniques, enhances the dispersability of soy protein products in water, while reducing discoloration in the soy protein products. Desirably, the new soybean processing technique will also continue to minimize off-flavors in the soy protein products, while maximizing destruction of antigenic substances. The process of the present invention provides a beneficial solution to these needs by yielding a product exhibiting enhanced solubility, reduced discoloration, minimized off flavors, and minimized antigenic protein content.